It is known in the art that a cam system, which may include, for example, a cam shaft and rocker arm, opens and closes a valve of an internal combustion (IC) engine. A standard cam profile engine valve opening/closing curve 300a is shown generally in FIG. 10 according to an embodiment.
It is also known in the art that the timing of engine valve closure during an IC engine's induction stroke may be varied to, among other things, optimize the performance of the IC engine. Known methods to achieve variable valve timing may include, for example, “lost motion” devices. A lost motion engine valve opening/closing curve is generally shown at 300c of FIG. 10. As illustrated, the lost motion curve 300c reduces (or may completely eliminate) the standard opening/closing stoke 300a of the engine valve.
However, there is often a desire to provide, among other things, a delayed, “added motion” closing stroke of an engine valve, which is shown generally at 300b. Fluid porting tolerances of a fluid actuator are stringently designed for controlling a delayed motion 301 and seating 302b of an engine valve along the added motion curve 300b. Due to, among other things, engine valve seating wear, the seating 302b may have undesirable performance variations, which are shown generally at 402. Such seating performance variations 402 may result from, for example, undesirable lash of an engine valve system.
A need therefore exists for providing an improved added-motion system and a lash adjustment mechanism and valve system that provides an expected seating performance as applied to, for example, an added motion engine valve.